This invention relates to appliances used for floor cleaning and the like. More specifically, the present invention relates to a means for adjusting the disposition of a vacuum cleaner carriage relative to a floor surface.
Vacuum cleaners of the floor cleaning or upright type generally include a chassis having a nozzle on a lower surface of a front end thereof through which air is sucked by an air moving motor-blower unit. A rotary brush is mounted adjacent the nozzle for contacting the floor surface to agitate and loosen dirt so that it may be sucked free of the surface. Wheels or other supports are rotatably mounted at the front and rear of the chassis for supporting the cleaner in a rolling manner on the floor. These vacuum cleaners are called upon to clean many different kinds of modern floor coverings varying in pile thickness from the short outdoor or patio-type carpeting to the long deep shag-type.
In order to clean these various floor surfaces effectively, it is known to vary the vacuum cleaner's nozzle height in order to locate the nozzle at a proper level above the surface to provide the required suction for the particular type of floor covering or surface being cleaned and to position the brush at the proper height. While many types of nozzle height adjusting mechanisms are known to the art, the known mechanisms are relatively complex and include a large number of parts because many nozzle heights are necessary to handle the different kinds of modern floor coverings available. The inherent multiplicity of such parts has made it more expensive to manufacture and assemble an upright vacuum cleaner.
One of the most common models of vacuum cleaners has a somewhat T-shaped housing which is supported on a widely spaced set of front wheels and a narrowly spaced set of rear wheels. The rear wheels are mounted on a carrier fork that extends rearward from a transverse horizontal pivot shaft. A height adjustment for this type of vacuum cleaner can be obtained through the use of a screw which is provided through a hole in the rear end of the rear housing and engages a cross brace on the rear wheel carrier fork. By manually turning the screw in one direction, the rear of the unit is lowered causing the floor cleaning nozzle to pivot about the front wheels in a downward direction. Turning the screw in the opposite direction allows the pivot shaft spring to raise the rear wheels and cause the floor cleaning nozzle to rise. When the manual turning of the screw produces the desired nozzle position, the rotation of the screw can be stopped.
Unfortunately, this type of height adjustment mechanism is time consuming to use and requires that the operator kneel down each time an adjustment needs to be made to the vacuum cleaner's height. Also, constant use of such a height adjustment mechanism, such as when the vacuum cleaner is used in an institutional setting, for example in a hospital, hotel or office building, will lead to the breakage of this conventional height adjustment mechanism.
Another problem with this known type of vacuum cleaner is that the rear wheel carrier fork sometimes jams against the underside of the vacuum cleaner housing beyond the maximum height adjustment position. This occurs most frequently when the vacuum cleaner is being pulled backwards and the rear wheels strike a raised section of the floor surface, such as the edge of a carpet. Although a pivot spring is provided to bias the carrier fork and prevent such doubling under, the spring often weakens with age or breaks thereby allowing this type of action to occur.
Accordingly, it has been considered desirable to develop a new and improved vacuum cleaner height adjusting mechanism which is mechanically simple, compact, durable in nature and which overcomes the foregoing difficulties and others while providing better and more advantageous results.